What are bulliform cells? What are their functions?

Bulliform Cells (Motor Cells)

• Definition & Location: Bulliform cells, also called motor cells, are large, bubble-shaped epidermal cells found in groups on the adaxial (upper) surface of monocot leaves. They are usually located near the midvein, appearing large, white, and colorless.

Function in Water Regulation

• In Adequate Water Supply: Bulliform cells remain turgid (swollen with water), keeping the leaf blade open and flat.
• During Water Stress: These cells lose water and shrink, causing the leaf to curl or fold inwards. This folding reduces the exposed surface area, thereby:
  • Reducing sunlight exposure
  • Lowering leaf heating
  • Minimizing water loss through evaporation

This adaptation helps plants conserve water in dry conditions.

Distribution

Bulliform cells are found in many monocot families but are most commonly associated with grasses.

Note

• The mesophyll is a chlorophyll-containing parenchymatous layer present between the upper and lower epidermis of a leaf.
• In monocot leaves, vascular bundles are collateral and closed, each surrounded by a bundle sheath made of thin-walled parenchymatous cells.